Heat transfer roll



W. H. NORTON ELM HEAT TRANSFER ROLL 5 Sheets-Sheet 1 m ai ec. H39 W6@Original Filed March 16, 1961 Dec. 13, 1966 w. H. NORTON HEAT TRANSFERROLL Original Filed March 16, 1961 Dec. 13, 1966 W, H. NORTON EQLZ-rHEAT TRANSFER ROLL Original Filed March 16, 1961 5 Sheets-Sheet 3 11VVEN TOR. ffl/idw? /7. Afa/'fon M M' l' Y ATTORNEYS United States PatentO 3 Claims. (Cl. 165-89) The present invention relates to improvementsin heat transfer rolls and. particularly to a roll which is internallyheated during normal operation and is rapidly and automatically -cooledat the termination of an operating run, and the present application is adivision of applicants copending application Ser. No. 96,313, led. March16, 1961, now U.S. Patent 3,216,489, issued November 9, 1965.

The present invention contemplates the provision of an electricallyheated heat transfer roll having a cylindrical outer shell and aconcentric inner shell forming a chamber therebetween containing a heattransfer fluid and preferably a eutectic composition. The roll isrotatably mounted on a hollow shaft wit-h electrical heating elementssupported on the shaft. The hollow supporting shaft is stationary andprovides a container :for electrical leads and a conduit for air. Anexhaust valve is positioned at one end of the shaft and low pressure andhigh pressure inlet valves at the other end of the shaft. The valves arepreferably electrically operated so that they can be switch controlledfor operation of the unit such as by a centrifugal switch. At the timeof start up the exhaust valve is closed and the interior of the roll ispressurized with a low pressure air and the heating elements areactuated. At the end of an operating run the exhaust valve is opened andhigh pressure air is blown through the drum through openings in theshaft for rapidly cooling the drum interior. Other operatingarrangements are possible as will `be described and the rapid coolingmay be effected by cooling coils embedded in the eutectic material.

An object of the invention is to provide an improved rotary heattransfer roll with improved effectiveness and efficiency well suited fora variety of manufacturing operations wherein a cylindrical heattransfer roll surface moves in engagement with a material to be heated.

Another object of the invention is to provide an improved heat transferroll construction having an increased margin of safety and well adaptedfor uses in the presence of materials which `are of an inflammable or anexplosive nature.

A still further object of the invention is to provide an improved heattransfer roll which can be very rapidly cooled when it is stopped sothat the temperature of the roll can be maintained above the temperatureof materials subject t-o thermal degradation for high speed operationand the roll immediately cooled when stopped to prevent damage to thematerial and the possibility of coniiagration or explosion. A stillfurther object of the invention is to provide an improved heat transferroll wherein uniform heating of the outer surface of the roll isobtained through the use of a eutectic composition.

Other objects and `advantages will become more apparent with theteaching of the principle-s of the invention in connection with thedisclosure of the preferred embodiments thereof in the specification,claims and drawings, in which:

FIGURE 1 is a vertical sectional view taken through the axial center ofa heat transfer roll embodying the principles of the invention;

fglll Patented Dec. i3, 1965 FIGURE 2 is a diagrammatic illustration ofa control circuit for the roll;

FIGURE 3 is a sectional view taken through the axis of a rool embodyinga lmodified arrangement `for rapidly cooling the roll;

FIGURE 4 is a vertical sectional view of a heat transfer roll with theinner `shell shown in `full to illustrate construction for obtaining auniform temperature along the roll;

FIGURE 5 is a vertical sectional view shown in somewhat schematic formof a roll standing on end illustrating steps in the method of fillingthe roll; and

FIGURE 6 is an enlarged detail sectional view of a portion of heattransfer roll insulating a construction for the outer shell.

As shown `on the drawings:

As illustrated in FIGURE 1, a heat transfer roll 5 includes a pluralityof shells, illustrated as including an outer shell 6 with a cylindricaloutwardly facing surface for engaging a surface to be heated. The rollincludes an inner -shell 7 which is illustrated as cylindrical andconcentric with the outer shell 6 and at the ends of the shells areannular end walls 8 and 9 which with the shells define a heatydistributor chamber 10. The chamber 1li is provided with a heatdistribution material which is preferably eutectic composition 10a. Theeutectic composition will be solid at normal room temperatures and willbecome liquid `at normal heating temperatures. A preferred eutecticcomposition will melt at 275 F. and will be usable to 1000 F. Othereutectic compositions are suitable and for certain conditions areuseable from 450 F. to 2000 F.

The eutectic materials will solidify at room temperatures and thereforethe problem of leakage when the machine is at rest is not present. Otherheat transfer fluids which tend to damage the materials with which theycome in contact are not used and the problems of providing positiveseals and inspection before usage are therefore avoided. Further, theeutectic composition is much easier to handle and store and the priceper pound is very appreciably less than other heat transfer uids. Theeutectic composition has a lower specific heat factor than other organicsubstances, which is an advantage. The eutectic composition has noboiling point and a Wider practical safe range of operation. It has agood conductivity factor, higher than liquid metal. For example, sodiumhas the highest conductivity factor of metals and of course would beunsafe for use. Sodium has a conductivity factor of 47 while a eutecticcomposition `suitable for use has a conductivity factor of 58. Aeutectic composition which has been used and found suitable and which iswithin the class of preferred eutectics is commercially available underthe trade name Quick Temper 275. The eutectic is inert, easy to handleand can be safely stored over a period of time. Another advantage is itsviscous properties, for example in the suitable heating range of 500 to700 F. The viscosity is higher than liquid metal, and the eutecticcomposition will adhere to the surfaces of the shells for improved heattransfer in the event air spaces are left.

The eutectic composition may be placed in the chamber 1t) when theshells are assembled or may be placed therein in the fluid state througha filling opening provided for that purpose. The chamber shown with apressure relief valve fitting 12 for the relief of internal pressureswhich may develop and the relief valve may be removable so that itsconnection can be used as a filling opening.

The eutectic material in the chamber 10 is preferably arranged so as notto completely till the entire void and to therefore leave an air spacefor expansion. In some circumstances it may be acceptable to use aliquid in the 3 chamber 10 instead of a eutectic composition. A liquidsuch as oil is suitable but must have a flash point above the operatingtemperature. The air space for expansion is shown at 10b and may be onlylarge enough to -permit normal heat expansion of the heat transfermaterial 10a in the chamber 10, inasmuch as the valve 12 will relieveundue expansion due to overheating or the like.

Within the rotor adjacent the inner shell 7 is a heating meanspreferably in the form of a plurality of tubular electric heatingelements 11. The heating elements are stationary and the rotor 5 ismounted for rotation about its axis on end support bearings 13 and 14.The heating elements are preferably of the tubular type with wireresistance elements embedded in compacted electrical insulating materialwithin the tubes, and extend axially within the rotor. As the rotor ismoved in rotation about the heating elements, heat energy is transmittedto the eutectic composition within the chamber to cause it to becomeliquid, and the liquid composition will evenly distribute the heatenergy to the outer shell 6.

The rotor and the heating elements are supported on a shaft 17 shown asbeing hollow to contain electrical conductors 18 which are connected tothe heating elements 11. The elements are stationarily supported attheir ends by radial support members and 16 which may be in the form ofspiders secured to the shaft. The support bearings 13 and 14 are alsomounted on the shaft.

For controllably regulating the heat of the rotor the electric currentto the heating elements 11 is controlled by a temperature responsiveswitch control member 19. This may be of the switch type or of theresistance thermometer type and the arrangement is shown schematicallyfor purposes of illustration in FIGURE 2.

The control 19 is electrically coupled to the circuit through slip ringand brush elements with the slip rings shown at 20 connected to leadsfrom the control 19 and with the brushes as shown at 21 connected to thecontrol circuit. Within the rotor 5 adjacent the inner shell 7 is aheating means preferably in the form of a plurality of tubular electricheating elements 11. The control circuit is shown in FIGURE 1 forpurposes of illustration only as including a control relay 19a which isomitted in FIG- URE 2. Electricity is supplied from the supply line 22.When the eutectic composition in the chamber reaches the desiredtemperature, the switch of the control 19 will open the circuit to theelectrical heaters 11, and as will be appreciated, various controlcircuits may be employed. A centrifugal switch 32 is employed to controlheating and cooling of the drum as a function of its rotation as will bedescribed.

The slip rings 20 and the brushes Z1 are shown as preferably locatedwithin the roll 5 so as to be surrounded by an atmosphere ofnon-explosive air, as will later be described.

The roll may be rotated by the friction of engagement with a surface tobe heated or may be driven in rotation at a suitable speed. Asillustrated, a pulley 23 may be attached to the end driven by a suitablebelt 24 which in turn is driven by a motor 25 operated by a motorcontrol 26 which determines the operation and speed of operation ofthemotor- As illustrated in FIGURE l, the roll 5 is provided with means forpressurizing the interior during operation to prevent the accumulationor entry of any combustible gases, such as might be given off bymaterial being heated. An air supply line 27 connects to the hollowshaft 17 and is supplied with a source of low pressure air forpressurizing the roll and is also provided with a source of highpressure air for cooling the roll rapidly at the termination of anoperating run. The low pressure source of air is controlled by anelectrically operated valve 28 connected to a low pressure source 32with a regulator valve 30 in the line. The high pressure air iscontrolled by an electrical valve 29 connected to a high pressure source33 and a regulator valve 31 is connected in the line. The

low pressure source 32 provides a high volume supply of air to establisha positive internal air pressure in the roll.

For example, a positive pressure of 3 pounds per square inch or more ofpure fresh air eliminates the possibility of accumulating an explosiveatmosphere within the roll. Wiring and connections are within the hollowshaft or within the roll and explosion-proof operation is thereforeaccomplished. The discharge of the hollow shaft 17 is provided with adischarge line 34 which is controlled by an electrically operated valve35. The valve 35 is closed during normal operation to permitpressurizing the roll.

The source 33 is a high pressure high volume source and supplies coolingair which flows through holes 36 into the roll. The air leaves throughholes 37 also communicating between the interior of the shaft and theroll and a partition 38 may be provided in the hollow shaft to insurethat the air will pass through the drum before it leaves through thedischarge valve 35. This supply of air is also used before beginningoperation to flush out the internal roll area and insure that the rollwill be filled with fresh air. As will be understood, the coolingeffects at the end of a run are completely compatible with the lowpressure explosion-proof operation. The air supply line 27 in thedischarge control valve 35 serve dual purposes in controlling flushingof the roll before operation, pressurizing the roll during operation,and cooling the roll at the end of an operation or when stopping.Flushing the interior with air immediately cools the heating elements 11and accomplishes a radical temperature reduction on the face of the rollat an accelerated rate in the order of 5 to 1 or as much as l0 to 1 asrelated to cooling timeunder static conditions, the cooling beingproportional to the total air ow rates provided.

The valves 28, 29 and 35 are preferably electrically actuated such as bya centrifugal switch 39. As illustrated in FIGURE 2, the electricalpower for the mechanism is derived from a main switch connected to thecentrifugal control switch 39 which is mounted on an end wall within theroll. The centrifugal switch is provided with multiple contacts so as tooperate the heating elements 11 and each of the valves.

As a typical operation, as the main switch 40 is closed, the centrifugalswitch 39 will open the exhaust valve 35 and the high pressure supplyvalve 29 so as to flush the interior of the roll 5 and exhaust anyaccumulated vapors. As soon as the roll starts moving, the centrifugalswitch closes the valve 35, closes the valve 29, energizes the heaters11, and opens the low pressure valve 28 to pressurize the interior ofthe roll. If desired, the centrifugal switch may first purge theinterior of the roll just as the roll starts rotating and the heatersmay be actuated as the roll reaches operating speed.

At the end of an operating run, as the roll is stopped or slowed downthe heaters 11 are de-energized and the valve 35 is opened while thehigh pressure valve 29 is also opened to discharge high pressure airinto the interior of the roll to effect rapid cooling.

Many materials are processed on heating rolls which are subject tothermal degradation. Inasmuch as material temperature is in relation ytosource temperature and dwell time, for practical operation rolls areoperated at a much higher temperature than is required in the processedmaterial. This permits higher take-off speeds and increased output.Whenever it is necessary to stop the roll it is necessary that itssurface temperature be immediately reduced below either the melt pointor a point of thermal degradation of the material as quickly aspossible. For instance, many rolls operating at 300 F. surfacetemperature, must be dropped to 200 F. quickly before shutdown to avoidserious damage to whatever material is being run. For example in runningmaterial webs, damage done during cool down forces the rejection oflengths of material. The longer period of cool down experienced, thelarger the cost of rejected materials. Of course, within limits, thetake-off speed can be reduced as the temperature falls so as to maintaina constant input value to the web during stopping. This could becontrolled by slowing down the motor by the motor control 26. Thepresent invention however contemplates cooling at an extremely rapidrate so that a correlation between speed and temperature does not haveto be maintained over any substantial shutdown.

In some instances, the centrifugal switch 39 can be replaced by orcom-bined with time delay relays so that the programming is primarilykeyed to time rather than rotational speed for shutdown. Various ratiosof time temperature and rotation are possible and are determined by thefactors of the material being run, actual speeds used and rate ofcooling of the roll. A timed operation is possible with the use of aclock although a centrifugal switch operating through relay controlseffects a saving in the price of equipment used.

ln the arrangement of FlGURE 3, a roll 5 has a construction similar tothat of FIGURE 1 but is cooled by liquid flowing through heat exchangecoils 41 embedded in the heat transfer eutectic between the outer shell6 and the inner shell 7 Liquid such as cold water is conveniently usedand a very rapid cooling is effected with the heat being removed fromthe surface of the outer shell 6 at a very rapid rate to effect almostinstantaneous cooling. With this type of cooling the heating elements 11need not be cooled, although the electrical energy is turned off, and acooling of the roll will be effected.

Cold Water coolant is supplied to the coils 41 through an inlet line 42which rotates with the roll 5 and is connected to a rotatable liquidconducting connector 45. The connector 45 may be in the form of arotatable outer jacket with a chamber 48 therein filled with water.Water is supplied to the chamber from a supply line 44. The water isdischarged at the other end of the drum through a line 43 connected to arotating connector 4d leading to a water discharge line 47. The waterwill usually be drained from the coils 41 for normal operation.

Cooling with the arrangement of FGURE 3 can be rapidly accomplishedwithout a flow of air and while maintaining the interior of the rollpressurized. Air pressurization is accomplished by an inlet line 49controlled by a valve 50 leading to the roll interior. An -outlet valve5l may be provided but is kept closed during operation. Valves 50y and51, and a valve 52 controlling the cooling liquid, may be controlledmanually or by timer operated switches, or yby a centrifugal switch 39.

As a brief summary of operation, with reference to FIGURE 1, at start-upthe electrical heating elements 11 are energized and high pressure airis flushed through the interior of the roll 5 by opening the valve 29and the exhaust valve 35. The exhaust valve 35 is then closed, and thehigh pressure valve 29 is closed and a low pressure valve 28 is openedto maintain the interior of the drum under pressure with clean freshair. Heat is transmitted uniformly to the outer surface of the roll 5through the eutectic material 10. At shutdown a rapid ow of cooling airis again admitted to the interior of the roll 5 by opening the valve 29and by opening the exhaust `valve 35 so that the material in engagementwith the roll will not be damaged when the roll is stopped.

Thus it will be seen that l have provided an improved heat transfer rollwhich meets the objectives and advantages above set forth. The roll iscompact and reliable in operation and employs simplified connections andcontrols which are reliable and which are explosion-proof.

While various eutectic compositions will be satisfactory in accordancewith the foregoing disclosure, a preferred eutectic is a mixture ofsodium and potassium nitrites and nitrates mixed to obtain a low meltpoint. This mixture will obtain a melt point of 275 F. or less and anoperating range of 275 F. to 1000o F. has been used. The resultanteutectic also obtains a high specific heat of approximately 0.4 which isdesirable in that it stores a substantial amount of energy. The thermalconductivity is also good being 58 B.t.u. per hour per foot per degreeFahrenheit. This conductivity is highly advantageous over organicmaterials, for example, and certain organics have a conductivity as lovlas 1/100 of this value. The cost of this eutectic mixture at currentprices is about 13da pound whereas other materials run substantiallyhigher in cost.` The boilnng point of this eutectic mixture runs up to1440" F. providing a good operating range. Boiling points on organic-s,and even fire resistant fluids are much lower. The material has beenused with various metals for the roll including aluminum, brass, copper,rubber and plastics, with silver solders and zinc plates and nocorrosion has occurred. The eutectic mixture does not have a flash pointwhich is objectionable in organic materials. In summary, this compoundhas been found to be advantageous from substantially all standpoints forthe purposes described.

FIGURE 4 illustrates a form or roll constructed for obtaining uniformityof temperature axially along the roll. The natural tendency of `a heattransfer roll is toward a hot center and c-old end. To overcome this aseries of fins are installed in the chamber to create a circulation ofheated eutectic from the center hot spot toward the ends which willobtain uniform temperat-ure along the ro-ll.

A roll 55 is shown in FIGURE 4 supported for rotation on a shaft 55 andprovided with a cylindrical outer shell 57 surrounding and spacedradially from a coaxial inner shell 58 in order to provide ia chamber 54therebetween. The chamber contains a 4heat transfer liquid such as aeutectic of the type describe-d above.

Mounted on the inner shell 5S are a series of outwardly projecting vanes59 and 60 which lprovide surfaces that `face outwardly in an axialIdirection so as to circulate eutectic axially. The helical vanes 59 and60 are arranged so that they exten-d in a direction from the center tothe end being wound in a direction opposite the direction of rotation ofthe drum which is indicated by the arrow 58a. Short spaces 61 and 62 arepresent between the -ends of the vanes and the end walls 57a of thechamber 54. The inner ends of the vanes are spaced apart in an axialdirection as shown by the ends 63, 64 and 65 for the vane-s 59. Thevanes extend successively further toward the center of the chamber S4 sothat each vane will catch a separate circumferential area of heattransfer liquid and in effect pump it outwardly. The vanes do not extendfully to the outer wall 57. The liquid will be pumped outwardly from thecenter and will lbe returned by circulating flow to the center forreheating. It will of course 'be understood that in some circumstancesit may lbe desired to secure the vanes to the inner surface of the outercylindrical shell 57.

FIGURE 5 is provided to illustrate a preferred method of filling theheat transfer roll of the invention. A roll 67 is shown with inner andouter shells to provide a chamber 63 for heat transfer fluid. A eutecticis lled into the chamber 68 preferably la mixture of sodium andpotassium nitrites and nitrates. Two openings 69 and 70 are provided inthe end of the chamber, one for filling and the other for permitting theescape of air.

The eutectic is provided from a heated container 71 which Iheats theimaterial to 400 F. This liquid material is filled into the opening 69as indicated by the filling line 72.

The chamber 68 is filled to a percentage of its full volume with thepercentage being critical. I have found that the chamber can be fil-ledto a volume ranging from 60 to 90% of the total volume and is preferablylled to substantially of its volume. As illustrated in FIG- URE 5, thechamber is lled to the level `represented by V1 which is in t-he rangeof `60 to 90%, and is preferably 80% of the total volume which Iisrepresented by VTi-V2. The remaining air space V2 of course will be inthe range of l to 40% of the total volume and will preferably be 20% ofthe total volume.

The eutectic is then permitted to cool and shrink and when cooled tosubstantially room temperature the openings 69 and 70 are closed so asto seal the chamber 68. At operating temperatures which aresubstantially ab-ove 400 F. the air in the space V2 will compress butwill not reach dangerous levels which would rupture the charmber 68.

For example in a chamber filled to 80% of total volume with the aboveeutectic at 400 F., and sealed, operation was conducted at an operatingtemperatureI of 670o F. at an internal air pressure of 26 pounds persquare inch. The original lling at 400 F. was convenient and eliminatedthe moisture from the chamber in the roll and from the eutectic.

FIGURE 6 illustrates a preferred construction for certain environmentsproviding a rolling surface having good heat transfer properties, havinga long wearing life, and being free from corrosive action from thermaterials enygaged -from the air. A roll 73 =has end walls 74 Vforsupporting an inner shell 76 with .a cylindrical concentric outer shell75. The shells are separated 'by an annular end wall 80 to form achamber 77 therebetween for heat transfer fluid. The outer shell isformed of layers and an inner layer 78 is preferably of metal and theouter layer 79 is of hard chrome.

Thus I have provided an improved apparatus and improved method whichmeets the objectives and advantages above set forth. The constructionpresents an improved land reliable heat transfer roll adapted fornumerous heat transfer 4operations wherein a surface must engage a heatreceiving surface without sliding friction and transfer heat energythereto.

It will be understood that the rolls 4, 5 and 6 are each provided withsuitable heating -means such as by electrical elements non-rotatablypositioned -in the rolls, similar to the structures of t-he otherfigures of the drawings. The rolls of FIGURES 5 and 6 are als-o providedwith suitable supports for rotatably supporting the rolls and this maybe done in any satisfactory manner as will be appreciated by thoseskilled in thev art.

The drawings and specification present a detailed disclosure of thepreferred embodiments of the invention, and it is to be understood thatthe invention is not limited to the speciic forms disclosed, but coversall modifications, changes and alternative constructions and methodsfalling within the scope of the principles taught by the invention.

I claim as my invention:

1. A heat transfer roll comprising:

an outer roll shell,

an inner roll shell concentric with said outer roll shell,

annular spacers spacing said roll shells apart and forming an annularliquid tight chamber containing a heat transfer liquid in the spacebetween said roll shells,

heating means heating the `inner of said roll shells and the heattransfer liquid in said annular chamber,

bearing means supporting said heat transfer roll for rotation,

at least two oppositely disposed helical fins within said chamber andextending radially of one of said shells toward the other shell andterminating in radially spaced relation with respect to the other shell,

said fins extending helically along said one of said shells in oppositedirections from locati-ons disposed on opposite sides of the transversecenter of said one of said shells toward said annular spacers, tocirculate the hot liquid toward the cooler ends of said outer shell andreturn the liquid toward the transverse center of said outer shell.

2. The structure of claim 1,

wherein at least two pairs of ns extend helically along said one of saidshells in opposite directions from locations disposed on opposite sidesof the transverse center of said one of said shells, toward said annularspacers and terminate in axially spaced relation with respect to saidannular spacers.

3. The structure of claim 1,

wherein at Vleast two pairs of tins extend `generally radially outwardlyof the inner of said shells in opposite directions from locationsdisposed on opposite sides of the transverse center of the inner of saidshells and terminate in substantial radial spaced relation with respectto the inner periphery of the outer of said shells,

and wherein the axial ends of said ns are spaced axially inwardly ofsaid spacers.

References Cited by the Examiner UNITED STATES PATENTS 2,875,985 3/1959Hold 165--89 2,956,348 10/1960 Mueller 165-89 X 2,980,403 4/1961 Ahlen165-90 3,074,695 l/l963 Hold et al. --90 X FOREIGN PATENTS 5,833 7/ 1903Denmark.

ROBERT A. OLEARY, Primary Examiner.

T. W. STREULE, IR., Assistant Examiner.

1. A HEAT TRANSFER ROLL COMPRISING: AN OUTER ROLL SHELL, AN INNER ROLLSHELL CONCENTRIC WITH SAID OUTER ROLL SHELL, ANNNULAR SPACERS SPACINGSAID ROLL SHELLS APART AND FORMING AN ANNULAR LIQUID TIGHT CHAMBERCONTAINING A HEAT TRANSFER LIQUID IN THE SPACE BETWEEN SAID ROLL SHEELS,HEATING MEANS HEATING THE INNER OF SAID ROLL SHELLS AND THE HEATTRANSFER LIQUID IN SAID ANNULAR CHAMBER, BEARING MEANS SUPPORTING SAIDHEAT TRANSFER ROLL FOR ROTATION, AT LEAS TWO OPPOSITELY DISPOSED HELICALFINS WITHIN SAID CHAMBER AND EXTENDING RADIALLY OF ONE OF SAID SHELLSTOWARD THE OTHER SHELL AND TERMINATING IN RADIALLY SPACED RELATION WITHRESPECT TO THE OTHER SHELL, SAID FINS EXTENDING HELICALLY ALONG SAID ONEOF SAID SHELLS IN OPPOSITE DIRECTIONS FROM LOCATIONS DISPOSED ONOPPOSITE SIDES OF THE TRANSVERSE CENTER OF SAID ONE OF SAID SHELLSTOWARD SAID ANNULAR SPACERS, TO CIRCULATE THE HOT LIQUID TOWARD THECOOLER ENDS OF SAID OUTER SHELL AND RETURN THE LIQUID TOWARD THETRANSVERSE CENTER OF SAID OUTER SHELL.